In episode 7 - A Feline House, Agemaki takes Zakuro to his family's estate on behest of his father's request to return home. When they enter, Zakuro senses a spirit and assumed that Agemaki had her come to do something about it. When she questions him, Agemaki gets scared that "it's still around".
Agemaki later reveals that the spirit Zakuro may have been sensing is possibly the one he saw as a child which scared him. After being scolded by his father, Agemaki noticed Itsue, his pet cat, gone and assumed the spirit had taken her and even begged for Itsue's return but to no avail.
Afterwards, Zakuro tells Agemaki that Itsue never disappeared, and we find out that the cat that Agemaki's little sister has is Itsue yet Agemaki can't see her. Itsue transforms, revealing that she is actually a Nekomata Spirit and that the spirit Agemaki saw as a child was Itsue in her normal form (looking much larger because of lighting and Agemaki's own size). Itsue transforms back, and Zakuro tells Agemaki that Itsue can't remain in her normal form for too long and he can't see her in her cat form because he can't sense spirits.
However, when Agemaki was a child, he could see Itsue all the time. He has always been afraid of spirits and didn't know Itsue was a Nekomata. I am wondering as to why Agemaki couldn't see Itsue afterwards?